KAM snaps are made from polyacetal resin, a type of plastic that is stronger and more durable than other types of plastic. Heart caps use the same die cap as rounds caps, size 20. These are great for diapers, bibs, different crafts, clothes, and scarves, anything you want to join together. There are numerous other uses for these snaps. Requires KAM Snap Pliers - Sold Separately